Method for determining the operability of a pressure sensor
A method for determining the operability of at least one pressure sensor of an internal combustion engine of a motor vehicle, in which the ambient pressure is first determined by the pressure sensor, and the ambient pressure determined by the pressure sensor is then compared to the ambient pressure determined by a reference pressure sensor not belonging to the internal combustion engine.
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The present invention relates to a method for determining the operability of at least one pressure sensor of an internal combustion engine of a motor vehicle.
BACKGROUND INFORMATIONDiagnostic methods meant to detect a malfunction of one or a plurality of pressure sensors are known from the related art. In systems using two pressure sensors the known diagnostic methods may cause the wrong sensor to be detected as faulty so that a properly working pressure sensor will be exchanged. This not only increases the cost for the workshop and the customer, since the vehicle may possibly have to be returned to the workshop a second time, but may also lead to a loss of image.
SUMMARY OF THE INVENTIONTo determine the operability of at least one pressure sensor in a flawless manner, the present invention provides that the ambient pressure is first determined with the aid of the pressure sensor, and that the determined ambient pressure is then compared to the ambient pressure determined by a reference pressure sensor which is not part of the internal combustion engine. If the ambient pressure determined by the pressure sensor conforms to the ambient pressure determined by the reference pressure sensor, then the pressure sensor is operative and working well. Of course, this assumes that the reference pressure sensor itself is working perfectly.
If the determined values of the ambient pressure do not agree, the pressure sensor is not operating properly, i.e., is not operative, and must be exchanged. The unambiguous determination of the operability of the pressure sensor prevents the exchange of a functioning pressure sensor.
To this end, the pressure sensor is advantageously situated in such a way that it detects the ambient pressure, i.e., on the outside of the internal combustion engine or on the outside of the housing of the internal combustion engine, for example, or at a suitable location inside the motor vehicle, such as the engine compartment.
In an advantageous manner, the pressure sensor is situated in an intake manifold of the internal combustion engine where it detects the ambient pressure when the internal combustion engine is switched off. During operation of the internal combustion engine, the pressure in the intake manifold would fluctuate and lie below the ambient pressure on average. To enable the pressure sensor disposed in the intake manifold to measure the actual ambient pressure, the internal combustion engine must therefore be switched off. The air in the intake manifold then does not move, and the pressure in the intake manifold corresponds to the ambient pressure.
Specifically, it is provided that the pressure sensor detects a charge pressure of a supercharger, in particular an exhaust-gas turbocharger, during operation of the internal combustion engine, and that it detects an ambient pressure when the internal combustion engine is switched off. The pressure sensor is a charging-pressure sensor, which measures the pressure of the precompressed air during operation of the internal combustion engine.
According to a further development of the present invention, a first pressure sensor is disposed in such a way that it detects the ambient pressure at all times, and a second pressure sensor is situated in the intake manifold of the internal combustion engine and detects the ambient pressure when the internal combustion engine is switched off. The two pressure sensors may be used to adjust the operation of the internal combustion engine to, for instance, a changed environmental air pressure, so that, for example, the internal combustion engine will continue to function properly even at high altitudes.
To check the operability of the pressure sensors, the ambient pressure detected by the first pressure sensor is advantageously compared to the ambient pressure determined by the second pressure sensor. Since the second pressure sensor detects the ambient pressure when the internal combustion engine is switched off, the two pressure sensors—provided they are functioning properly—should determine the same ambient pressure. If the determined ambient pressure of the first pressure sensor deviates from the ascertained ambient pressure of the second pressure sensor by more than the known sensor tolerances, for example, then a malfunction has occurred in one of the pressure sensors.
In order to determine which one of the two pressure sensors is defective, the ambient pressure determined by the first pressure sensor or the ambient pressure determined by the second pressure sensor is advantageously compared to the ambient pressure detected by the reference pressure sensor. If the determined values for the ambient pressure match, then the pressure sensor not taken into account in the comparison is faulty. If, for instance, the ambient pressure determined by the first pressure sensor is compared to the ambient pressure determined by the reference pressure sensor, and if the determined values agree, then it follows that the second pressure sensor is not working properly, due to the fact that one of the two pressure sensors had already been determined to be faulty in the previous step. Thus, it is sufficient here to compare one of the two pressure sensors to the reference pressure sensor to determine the faulty pressure sensor.
According to a further development of the present invention, the ambient pressure determined by the first pressure sensor and the second pressure sensor is compared to the ambient pressure determined by the reference pressure sensor. In this way it can be ensured that not both pressure sensors are operating in a faulty manner. Furthermore, this is an especially simple approach for checking both pressure sensors with regard to their operability since it is not necessary to first compare the ambient pressure determined by the first pressure sensor to the ambient pressure determined by the second pressure sensor. As already mentioned, this of course assumes that the reference pressure sensor is operating properly.
In principle, this method also makes it possible to check a pressure sensor which measures a charging pressure of a supercharged internal combustion engine. A prerequisite is that the pressure sensor (charging-pressure sensor) measures an ambient pressure when the internal combustion engine is switched off.
All methods require that the sensor tolerances be taken into account in order to avoid the replacement of pressure sensors or reference-pressure sensors that are functional according to their specification.
Claims
1. A method for determining an operability of at least one pressure sensor of an internal combustion engine of a motor vehicle, comprising
- using a first of the at least one pressure sensor to detect a charge pressure of an exhaust-gas turbocharger during operation of the internal combustion engine;
- using the first pressure sensor to detect an ambient pressure when the internal combustion engine is switched off, the detection of the ambient pressure including determining a first ambient pressure value;
- comparing the first ambient pressure value to a second ambient pressure value determined by a reference pressure sensor not belonging to the internal combustion engine; and
- determining a fault in the at least one pressure sensor in response to detection in the comparing step of a difference between the first and second ambient pressure values.
2. The method according to claim 1, wherein the first pressure sensor is situated in such a way that it detects the ambient pressure.
3. The method according to claim 1, wherein the first pressure sensor is situated in an intake manifold of the internal combustion engine.
4. The method according to claim 1, wherein a second of the at least one pressure sensor is situated in such a way that it detects the ambient pressure at all times, and the first pressure sensor is situated in an intake manifold of the internal combustion engine.
5. The method according to claim 4, wherein the second pressure sensor is situated on an outside of the internal combustion engine.
6. The method according to claim 4, wherein the second pressure sensor is situated on an outside of a housing of the internal combustion engine.
7. A method for determining an operability of at least one pressure sensor of an internal combustion engine of a motor vehicle, comprising:
- using a first of the at least one pressure sensor to detect a charge pressure of an exhaust-gas turbocharger during operation of the internal combustion engine;
- using the first pressure sensor to detect an ambient pressure when the internal combustion engine is switched off, the detection of the ambient pressure including determining a first ambient pressure value, wherein a second of the at least one pressure sensor is situated in such a way that it detects the ambient pressure at all times, and the first pressure sensor is situated in an intake manifold of the internal combustion engine;
- in a first comparing step, comparing the first ambient pressure value to a second ambient pressure value determined by the second pressure sensor;
- in a second comparing step, comparing at least one of the first ambient pressure value and the second ambient pressure value to a third ambient pressure value determined by a reference pressure sensor not belonging to the internal combustion engine; and
- identifying a fault in the at least one pressure sensor in response to detection in the second comparing step of a difference between the at least one of the first and second ambient pressure values and the third ambient pressure value.
8. The method according to claim 7, wherein only one of the first and second ambient pressure values is compared to the third ambient pressure value in the second comparing step.
9. The method of claim 7, wherein the identifying the fault is based on the first comparing step.
10. The method of claim 7, wherein the second comparing step and the fault identification are performed conditional upon determining a difference between the first and second ambient pressure values in the first comparing step.
11. A method for determining an operability of at least one pressure sensor of an internal combustion engine of a motor vehicle, comprising
- using a first of the at least one pressure sensor to detect a charge pressure of an exhaust-gas turbocharger during operation of the internal combustion engine;
- using the first pressure sensor to detect an ambient pressure when the internal combustion engine is switched off, the detection of the ambient pressure including determining a first ambient pressure value, wherein a second of the at least one pressure sensor is situated in such a way that it detects the ambient pressure at all times, and the first pressure sensor is situated in an intake manifold of the internal combustion engine;
- comparing the first ambient pressure value and the second ambient pressure value to a third ambient pressure value determined by a reference pressure sensor not belonging to the internal combustion engine; and
- identifying a fault in the at least one pressure sensor in response to detection in the second comparing step of a difference between at least one of the first and second ambient pressure values and the third ambient pressure value.
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Type: Grant
Filed: Sep 11, 2007
Date of Patent: May 4, 2010
Patent Publication Number: 20080066522
Assignee: Robert Bosch GmbH (Stuttgart)
Inventors: Christof Thiel (Heilbronn), Andreas Bethmann (Ditzingen)
Primary Examiner: Thomas P Noland
Attorney: Kenyon & Kenyon LLP
Application Number: 11/900,447
International Classification: G01L 27/00 (20060101);